Method and Structure for Cooling an Electric Motor

ABSTRACT

A high speed electric motor for use in a variety of applications. The electric motor an electric motor including a motor housing or stator, a rotor having a commutator and brushes for contacting the commutator at a predefined area known as the contact area. Additionally, the motor includes a forced air cooling assembly. The forced air cooling assembly includes a centrifugal fan for creating air flow, a manifold for accelerating the air flow. The manifold having exit ports and the exit ports being positioned directly over the contact area for directing the accelerated air flow at the contact area and the motor housing having at least one opening aligned with the contact area and at least a second opening defining an exit vent. Additionally, a method of cooling the motor in accordance with the invention is also disclosed.

REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 13/103,301, which has nowbeen allowed and which shall issue as patent in due course. Thatapplication is a continuation of U.S. Pat. No. 7,804,208. Other thanthis paragraph, the only changes made to the application as originallyfiled are those set forth in Response A of the parent case with respectto the section “In the Specification” as well as certain typographicalerrors which have been corrected. No new matter has been added.

FIELD OF THE INVENTION

This invention generally relates to the field of brushed electricalmotors. More particularly, this invention relates to small, high speedelectric motors, which include structure for internal cooling.

BACKGROUND OF THE INVENTION

Electric motors are in widespread use for a seemingly never endingvariety of tasks. Such motors are popular because they are small andpowerful. Additionally, there is virtually zero pollution and generallyspeaking the motors run far more quietly than other motors, such as aninternal combustion engines (ICEs). Many industries rely solely uponsuch electrical motors to power their devices. For example, poolcleaners are virtually exclusively powered by such motors. As will beappreciated, in order to make such devices practical, the motors must bequite small and very powerful. Such motors are required to rotate atextremely high speed and are placed in a confined spaces. As will bereadily understood the physical limitations of such spaces and the highspeed of the motors means that heat build up can be extreme, especiallywhen such motors are put to constant and heavy usage.

The two weakest points to such small high speed electric motors in aconfined space are heat which catastrophically damages the copperwindings of the motors and dust or particulate matter build up on thecommutator, especially at the contact area between the brushes and thecommutator which likewise causes catastrophic failure. Heat causes theCopper wiring of the armature to become so hot it fails to function andthen fails catastrophically so that the motor is permanently damaged andneeds to be replaced. Thus, heat is the primary enemy of such motors andthere is a long felt need to cool such motors.

Next is dust or particulate matter. For example, most brushes are madeof graphite. Contact between the brushes and the commutator is requiredto complete the electromagnetic circuit and thus essential for motoroperation in a brushed motor environment. As the brushes contact thecommutator, wear occurs and very fine graphite particles, dust, in fact,escape into the air and also build up on the commutator at the contactarea between the commutator and the brushes. When enough suchparticulates build up on the commutator, the brushes will fail tocomplete the electromagnetic circuit and the motor will no longeroperate.

Clearly no motor lasts forever. However, in the case of brushedelectromagnetic motors it would approach optimum if the motor life couldbe extended at least as long as the brush life. In practice, it has beenfound that typically first, the copper wire fails cutting motor life asthe result of excess heat. And, subsequently, should the user be able toget by copper wire failure, dust or particulate build up, especiallyfrom graphite dust, similarly causes catastrophic and permanent failure.

As stated above, there is a long established need to cool electricalmotors. This is especially true for brushed electrical motors, which aresubject to long continuous and constant usage on a daily basis. In fact,a quick review of the US/PTO records shows that there are over a hundredreferences concerned with the cooling of electrical motors.

Most of the references found in the US/PTO are for liquid cooleddevices.

Typically, these devices are non-brushed motors such as inductionmotors. Non brushed motors are also known as brushless motors. Brushlessmotors do not require a brush nor do they require physical contact ofthe brush with the commutator in order to make electrical contact andcause the motor to operate. Brushless motors use a dielectric fluid ascooling media.

With respect to the brushed motors references, typically air is used theas cooling media. Typically, the brushed motor references related tocooling focus on improving cooling by integrating a heat sink on themotor housing. In virtually all cases disclosed, an axial fan is used tocool and is integrated as part of the motor or separately connected.Such an axial fan draws air and pushes air towards the motor housing andattempts to provide cooling. However, whether integrated or separatedfrom the motor, an axial fan provides high air flow but low airpressure.

U.S. Pat. No. 7,042,121 discloses an electrical motor having a coolingair flow generated by a fan wheel and routed through ventilationopenings of the motor housing. The motor further includes a heat sinkand a fan to aide in additional cooling,

For example, U.S. Pat. No. 4,092,556 discloses a closed system forcooling an electric motor that includes a rotor, a stator and acommutator. The motor includes ducts, which have openings opposite thesurface of contact of the brushes and the commutator. Air is forcedthrough the ducts from either side of the rotor on the contact. The fanfrom the air is directed through a cooling path by cooling elements anddesigned to increase cooling flow and add effective cooling to themotor. The cooling elements are external to the motor.

Thus what is needed is a motor, which lasts as long as the brushes,while being able to provide high speed operation in a confinedenvironment. As explained below, the instant invention provides anapparatus and method, which provides adequate cooling to extend motorlife through preservation of the cooper windings and by clearing thecontact area of graphite build up.

SUMMARY OF THE INVENTION

A method and structure for cooling a small high powered electricalmotor, which includes the motor in accordance with the invention havingcooling structure. The cooling structure provides forced and pressurizedair at the area of contact between the brushes and the commutator. Theair hits the commutator contact area with enough force to cool thecopper wires and dislodge particulates, notably graphite particles fromthe contact area.

It is an object of this invention to provide a method and structure forcooling a small high powered electrical motor.

It is an additional object of this invention to provide such a methodand structure for cooling a small high powered electrical motor, whichdislodges graphite particles from the contact area between the brushesand commutator to extend the life of the brushes.

It is an additional object of this invention to provide a method andstructure for cooling a small high powered electrical motor, whichextends the life of the motor by extending the life of the brushes.

The motor in accordance with this invention employs a centrifugal fan tocompress and blow air towards the commutator. In one exemplaryembodiment, the fan comprises an impeller. The impeller forces the airflow towards the armature and in particular toward the contact area.Forced air cools as it passes through motor housing and along the heatgenerating components. Particularly, the forced and pressurized airflows past the heat generating components including the brush, thecommutator, and copper windings as well as the armature causing coolingas it goes.

Additionally, the air flow is of sufficient strength and pressure todislodge particulates. Particularly, the brushes of such motors are madeof graphite. Small bits of graphite defining dust particles cause buildup on the contact area. By providing such a flow of air that dislodgesparticulates, including graphite dust from the contact area, particulatebuild up at the contact area is discouraged, if not eliminated.Additionally, it will be appreciated that a commutator having a dirtycontact area will lower the motor efficiency. Further, such a dirtycontact area will likely generate extra heat due to a partial shortingof the circuit between the commutator and the brushes.

In accordance with one exemplary embodiment of the motor of theinvention, which comprises:

-   -   an electric motor having a motor housing, a stator, a rotor        having a commutator and brushes for contacting the commutator at        the contact area;    -   a forced air cooling assembly including:    -   a fan for creating air flow;    -   a manifold for accelerating the air flow;    -   the manifold have exit ports and the exit ports being positioned        directly over the contact area for directing the accelerated air        flow at the contact area; and    -   the motor housing having a plurality of opening; at least one        opening aligned with the contact area and at least a second        opening defining an exit vent.

In another exemplary embodiment, the electrical motor in accordance withthe invention includes a manifold having two impeller exit ports whichare opposed from one another and having contact area intakes and they,too, are opposed from one another.

It is an advantage of this invention to provide such an electricalmotor, which increases motor life in a confined environment.

BRIEF DESCRIPTION OF THE DRAWING

For a further understanding of the objects and advantages of the presentinvention, reference should be had to the following detaileddescription, taken in conjunction with the accompanying drawing, inwhich like parts are given like reference numerals and wherein:

FIG. 1 is a partially cut away perspective view of the electrical motorin accordance with this invention.

FIG. 2 is a partially exploded view of the electrical motor inaccordance with this invention showing detail of one exemplary manifold.

FIG. 3 is an enlarged cross sectional view of the reverse side of themanifold of the electrical motor in accordance with this invention.

FIG. 4 illustrates the air flow from the impeller to the exit vents inthe motor housing in accordance with electrical motor of this invention.

FIG. 5 illustrates the electrical motor of this invention in use.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of the electric motor in accordance with thepresent invention generally denoted by the numeral 20 will now bedescribed with reference to FIG. 1. The motor 20 includes a stator 22 orhousing, an armature 24 or rotor and a brush assembly, generally denotedby the numeral 26.

The armature 24 includes a commutator 28. Typically, the commutator 28uses copper segments. However, more modern examples of the commutator 28include graphite segments.

The brush assembly 26 includes a brush holder 30 for holding a brush 32against the commutator 28. The area which the brush 32 contacts thecommutator 28 is called the contact area.

The brush holder 30 holds the brush 32 in place and provides electricalinsulation from the housing when the rotor is activated. Supplying powerto the motor causes the brush 32 in contact the commutator 28 at thecontact area to complete the electrical circuit and cause the armatureto rotate.

The exemplary embodiment 20 further includes a forced air coolingassembly generally denoted by the numeral 40 (FIG. 2). The forced airassembly includes a fan defining an impeller 42, a manifold 44 and ventshafts 46.

A partition 48 separates the impeller 42 from the motor housing 22. Thepartition 48 in an exemplary embodiment is made of plastic. In anotherembodiment, the partition 48 is made from a printed circuit board (PCB).Using this embodiment of the partition 48, motor leads are connected thePCB. Additionally, the partition 48 of this embodiment because it is aPCB is attached directly to the motor housing.

The impeller 42 is mounted on the rotor 24 and separated from the motorhousing 22 by the partition 48. The manifold 44 is mounted over theimpeller 42 and onto the partition 48. It will be appreciated that sincethe manifold 44 is mounted over the impeller 42, the inside opening ofthe manifold 44 is larger than the impeller 42. This allows pre-assemblyof the motor before the installing the impeller 42.

The manifold 44 is fixed to the partition 48 and immobile thereto by alocking member 50. The locking member 50 includes a male member 54,which is threaded through an aperture 52 n the manifold 44. The malemember 54 locks into the partition 48 holding manifold 44 in place.Additionally, the locking member 50 is used to close the inlet to themanifold 44 as appropriate.

As shown in FIGS. 2 and 3, the manifold 44 includes a collar 56. Thecollar 56 has impeller exit ports 58. As the impeller rotates, itcreates a stream of air, which is forced out the exit ports 58. Theforced air travels at an accelerated rate of speed through the ventshafts 46 as a result of being circulated first through the manifold 44.

The accelerated air flow is also pressurized as a result of the highspeed of the impeller 42 and as a result of being forced through exitports 58. The pressurized air flow enters the side vents 46 and thenflows through to the housing 22.

The housing 22 has a plurality of openings. At least one of one of theopenings, opening 62 is positioned directly adjacent the contact areaand defines an intake port for directing the air flow to the contactarea. In the exemplary embodiment shown in FIG. 2, the opening is shapedas a slot and acts to further direct the air flow toward the contactarea.

In another embodiment, the impeller 42 is offset from the motor rotor.In this embodiment, the air blows directly onto the motor housing 22without additional manifold or vents. Since the impeller 42 is offset, aset of pulleys and gears is used to power the impeller 42.

It will be appreciated that in one exemplary, the opening 62 ispositioned directly adjacent the contact area. However, as will beappreciated the intake port may be located somewhat differently withinthe spirit and scope of the invention. It will be appreciated that theonly limitation is that there be an air flow with sufficient force tocool the motor parts and dislodge graphite and other particulates fromthe commutator.

With respect to FIGS. 4 & 5, there is shown the air flow patternincluding the direction. Upon cooling the motor parts, e.g. the copperwiring and the commutator, especially at the contact area and dislodgingparticulates from the commutator contact area, the air flow exits themotor housing 22. The air flow exits through vents 70.

In the exemplary embodiment illustrated in FIG. 2, there are two vents70. However, it will be appreciated that the number of vents is notcritical as long as the air flow is vented thoroughly through thehousing 22. There must be sufficient venting to a allow a continuousflow of pressurized air through the motor housing 22.

With respect to FIG. 5, there is shown an exemplarily embodiment of themotor 20 in accordance with the invention in use. The motor 20 in thisapplication is encased in a water tight housing 80. The rotor 24includes a gear 82, which rotates as the motor 20 rotates. The gear 82,in the instant application acts as a pinion gear and in turn rotatesgear 84, which in turns rotates propeller 86. in use with a poolcleaner, for example, the propeller is used to move the pool cleanervehicle along the underwater surfaces of the pool.

While the foregoing detailed description has described severalembodiments of the electrical motor in accordance with this invention,it is to be understood that the above description is illustrative onlyand not limiting of the disclosed invention. Particularly, there can bea variety of intake ports and exit vents that are all within the spiritand scope of this invention. It will be appreciated there are alsovarious impeller type fans that are suitable for use in the exemplaryembodiments discussed above and that there are numerous embodiments thatare not mentioned but within the scope and spirit of this invention.Thus, the invention is to be limited only by the claims as set forthbelow.

What is claimed is:
 1. A small, high powered, electrical motor havingforced air cooling, comprising: an electric motor having a motorhousing, a stator, a rotor having a commutator and brushes forcontacting the commutator defining a contact area; a forced air coolingassembly including: a fan for creating air flow; a manifold foraccelerating the air flow; the manifold having exit ports and the exitports being positioned directly over the contact area for directing theaccelerated air flow at the contact area; and the motor housing having aplurality of opening; at least one opening aligned with the contact areaand at least a second opening defining an exit vent.
 2. The electricalmotor of claim 1, wherein the fan for creating the air flow defines ancentrifugal fan.
 3. The electrical motor of claim 2, wherein the fan forcreating the air flow defines an impeller.
 4. The electrical motor ofclaim 3, wherein the impeller creates the air flow and the manifoldpressurizes and accelerates the air flow.
 5. The electrical motor ofclaim 4, wherein the impeller is attached to the rotor and rotates asthe motor rotates forcing pressurized air through the manifold and ontothe contact area.
 6. The electrical motor of claim 3, wherein themanifold defines at least one an impeller exit port and at least onecontact area intake for directing air flow directly onto the contactarea.
 7. The electrical motor of claim 6, wherein the manifold has twoimpeller exit ports and they are opposed from one another.
 8. Theelectrical motor of claim 7, wherein the manifold has two contact areaintakes and they are opposed from one another.
 9. The electrical motorof claim 9, wherein the two impeller exit ports are 180 degrees opposedand the two contact area intakes are also 180 degrees opposed from oneanother.
 10. The electrical motor of claim 9, wherein one pair ofimpeller ports and contact area intakes are in-line with one another and180 degrees opposed to the other port and intake pair.
 11. Theelectrical motor of claim 1, wherein the manifold includes a collarconnected to one end of the motor housing and a passageway defining avent shaft defining the distribution means for delivering the air flowcreated by the impeller from impeller exit port to the contact areaintake.
 12. The electrical motor of claim 11, wherein the vent shaft isattached removably to the collar.
 13. The electrical motor of claim 8,wherein one end of the vent shaft is positioned and is in opencommunication with the impeller exit port and the other end of the ventshaft is in open communication with the contact area intake.
 14. Theelectrical motor of claim 1, wherein impeller is offset from the rotor,and the impeller is powered by a set of gears and a pulley connected tothe rotor.